1. Field of the Invention
The present invention relates to an apparatus for controlling operation of an internal combustion engine in a hybrid vehicle with the internal combustion engine and a motor mounted thereon. More specifically the present invention pertains to an apparatus for controlling the driving state of the internal combustion engine during an inspection of the operation of the internal combustion engine mounted on the hybrid vehicle.
2. Description of the Related Art
There are two types of hybrid vehicles; one type with an engine that is applicable as a driving source of the vehicle (parallel-type hybrid vehicle) and the other type with an engine that is not directly applicable as a driving source of the vehicle but is mainly used to drive a generator (series-type hybrid vehicle). Both types of the hybrid vehicles can run using only a motor as the driving source while the engine is at a stop. The parallel-type hybrid vehicle uses the engine as the main driving source during a normal run, but may be driven under the ceased condition of the engine. The latter condition is applied when the engine power is not required, for example, during reduction of speed and during a drive on a down-slope, and when a drive with the motor is more suitable than a drive with the engine, for example, at the time of initial acceleration. The series-type hybrid vehicle starts and stops operation of the engine according to the charging state of the battery which supplies electric power to the motor. By way of example, when the remaining charge of the battery is lowered, the engine is driven to activate the generator and charge the battery. When the battery has the sufficient remaining charge, on the other hand, operation of the engine is stopped even during a drive. In the hybrid vehicle, even under the active state of a starter switch, the engine starts and stops operation according to the remaining charge of a storage battery and the driving conditions of the vehicle. In the conventional vehicle with only the engine as the driving source, the engine keeps driving unless the starter switch is turned off. This is one of the main differences between the hybrid vehicle and the conventional vehicle with only the engine as the driving source.
It is required to inspect the engine periodically or at the time of malfunction in the hybrid vehicle as well as the conventional vehicle with only the engine as the driving source. The engine mounted on the hybrid vehicle essentially has the same structure as that of the engine mounted on the conventional vehicle. The process of inspecting the operation of the engine in the conventional vehicle is accordingly applicable to the hybrid vehicle. The process of inspecting the operation of the engine in the conventional vehicle is described briefly with the drawing of FIG. 9.
FIG. 9A schematically illustrates one arrangement in an engine room in the conventional vehicle. An engine 150a, an EFIECU 170a for controlling the operation of the engine 150a, a diagnosis connector 172a used for inspection of the engine 150a are included in the engine room. The diagnosis connector 172a is an essential element used for the inspection of the engine 150a.
FIG. 9B is an enlarged view illustrating the diagnosis connector 172a. As shown in FIG. 9B, terminals of the diagnosis connector 172a are connected to each other via a check wire 240a for inspection of the engine 150a. The terminals to be connected are selected according to the item of inspection. FIG. 9C is a plan view illustrating the diagnosis connector 172a. By way of example, for inspection of the ignition timing of the engine 150a, terminals T and E shown in FIG. 9C are connected to each other via the check wire 240a. The terminal T is connected to a signal input unit of the EFIECU 170a and is generally pulled up to a predetermined voltage in the EFIECU 170a. Connection of the terminal T with the terminal E causes the terminal T to be grounded. At a normal run, the EFIECU 170a drives the engine 150a while varying the ignition timing of the engine 150a according to the revolving speed of the engine 150a. In case that the voltage of the terminal T is equal to the grounded voltage, on the other hand, the EFIECU 170a drives the engine 150a while fixing the ignition timing to a predetermined standard ignition timing. When the engine 150a is driven in this state, the standard ignition timing may be measured and regulated. Other inspection items carried out under the connecting state of the diagnosis connector 172a include reading the ratio of air to fuel (the air/fuel ratio) when the engine 150a is at an idle and reading the diagnosis code representing the failure of the engine 150a. These inspections are carried out while the terminal T is linked with the terminal E.
Some items of inspection of the engine 150 are carried out without connecting any two terminals of the diagnosis connector 172a. One example of such items is inspection of exhaust, which determines whether or not the concentrations of toxic components, such as CO and HC, included in the exhaust from the engine 150 satisfy predetermined criteria. As mentioned above, when the terminal T and the terminal E of the diagnosis connector 172a are connected with each other, the engine 160a is driven at the standard ignition timing that does not depend upon the revolving speed of the engine 150a. This means that the engine 150a is driven under the driving conditions different from those at a normal run. The inspection of the exhaust should, however, be carried out under the same conditions as those at a normal run. It is accordingly required to drive the engine 150 at a predetermined revolving speed and carry out the inspection without connecting any two terminals of the diagnosis connector 172a. Another inspection item carried out without connecting any two terminals of the diagnosis connector 172a is measurement of the idling speed of the engine 150a.
In the hybrid vehicle, it is required to drive the internal combustion engine in a variety of driving states at the time of inspection of the operation of the internal combustion engine. As discussed previously, however, the hybrid vehicle stops the operation of the internal combustion engine when predetermined conditions are fulfilled, for example, when the battery has sufficient electric power. In some cases, the internal combustion engine stops its operation at the time of inspection according to the charging state of the battery. This causes troubles in inspection. This problem is characteristic of the hybrid vehicle and does not arise in the conventional vehicle with only the internal combustion engine as the driving source.